1. Field of Invention
This invention relates to folding or collapsible cots or beds, particularly those used in camping and expeditions.
2. Description of Prior Art
The typical lightweight camp cot consists of three parts:
(1) A rectangular body-support sheet (the top); PA0 (2) A pair of long side rails to hold the sheet; and PA0 (3) Two or three transverse leg assemblies to hold the side rails.
The combined weight of these parts is frequently less than ten (10) pounds.
"End bars" are notably absent from the lightweight camp cot. Their cross-bracing function has been assigned to transverse leg assemblies located entirely below the plane of the body-support sheet.
Sleeping comfort on the camp cot is largely dependent on the flatness and firmness of the body-support sheet, which in turn, is dependent on the tensioning force applied to the sheet.
One fixed tension setting cannot satisfy all users because of differences in body weight and personal preferences. For individual comfort, the force applied to tensioning the body-support sheet must be variable, that is, easily adjusted by the user.
Means have been devised to vary tension in the length dimension of the body-support sheet (much as a hammock is stretched from end to end) and also in the short or cross dimension (pulling the body-support sheet from side-to-side.)
Of the two, crosswise tensioning of the body-support sheet appears more suitable for control of sheet flatness.
In pursuit of crosswise tensioning several means have been developed, all adjusting the overall width of the entire transverse leg assembly. By making the transverse leg assembly wider, the distance between side rails is increased and the body-support sheet is stretched tighter.
U.S. Pat. No. 1,929,000 (John M. Line) shows an early example of such crosswise tensioning. The horizontal portion of the transverse leg assembly consists of two overlapping angle irons. One angle iron is provided with a series of spaced slots, and the other with a locking tongue. The cot user places the tongue in a selected slot, hooking the two angle irons together. If the resulting tension on the body-support sheet is inadequate, the whole width of the transverse leg assembly is again increased by the selection of a different slot.
In U.S. Pat. No. 2,639,442 (Eduard Herzoo) the same objective is accomplished by using two horizontal telescoping tubes in a modified U-shaped transverse leg assembly. The larger tube is provided with a series of spaced holes, and the smaller tube with a spring-loaded pin. Tension adjustment consists of selection of a particular hole for the pin to engage.
In U.S. Pat. No. 3,956,781 (Otto M. Reemelin) the whole U-shaped transverse leg assembly is again adjustable in width. However, in this case the two horizontal leg members do not interlock directly, but rather through a shared "central link". Each horizontal leg member has a series of spaced notches, and the central link has a pin at each end to engage the notches. Selecting any two notches to hook on the pins determines the width of the transverse leg assembly.
Two disadvantages become apparent in tensioning a body-support sheet crosswise by altering the entire width of the transverse leg assembly, as is done in the three cases cited above:
1. It is inconvenient for the user to adjust tension. The user must turn the cot over or on its side, release locking devices, relocate horizontal members against fabric resistance, and lock the members again in a new position.
2. It is impossible for the user to vary tension except in the fixed increments provided by the manufacturer's spacing of slots, holes, or notches. There is no allowance for "fine tuning".
In addition, there is a generic weakness in many cots with lightweight, flexible transverse leg assemblies: To the eye of the user, a flat-appearing body-support sheet may seem like an ideal bed, but, when body weight is applied, the body-support sheet sags, and further adjustment is necessary.
Thus, while crosswise tensioning is such a promising concept, means have been lacking to make it convenient, finely-adjustable and accurately predictable.